Sam and Ethel had five living children (possibly more? not sure): Samuel Edwin, b. 1920 in Van Buren, Ark. Neva C, b. 1924 in Ark. Charles Wayne, b. 1930 (unsure where) Dorla Jean, b. 1932 (unsure where) George Robert, b. 1933 (death cert. says born in Okmulgee County, Oklahoma)
I also know that Sam and Ethel were divorced some time after George was born. Also, some time after George's birth, the family moved to the Detroit, Michigan area, if that's helpful for you.
Like I said in my original post, I found a 1910 census from Arkansas with a Samuel E Thompson (who was 9 at the time of the census, putting him at the same age as my Sam Thompson), but I have no idea if that Samuel Thompson is my Sam(uel?) Thompson.